before another took its place."
The professor remained thoughtful and silent.
"Is it not by the light which comes from them that we have gained all our knowledge of the constitution of the heavenly bodies?" I continued. "A ray from the remotest star brings in its heart a secret message to him who can read it. Now, the Martians would naturally resort to the same medium of communication as the most obvious, simple, and practicable. By producing a powerful light they might hope to attract our attention, and by imbuing it with characteristic spectra, easily recognised and changed at intervals, they would distinguish the light from every other, and show us that it must have had an intelligent origin."
"We should know that the Martians had a civilisation at least as high as our own. To my mind, that would be a great discovery--the greatest since the world began."
"But of little use to either party."
"As for that, a good many of our discoveries, especially in astronomy, are not of muc